Think your magic is mondo cool? Think again, sucka.
Magic Rule 1: Having magic powers and the Magic Materialization ability isn't god-mode. You aren't Bugs Bunny. There are limitations to what you can do.
Magic Rule 2: Magic is tiring to use, just like ki. Even an accomplished wizard would have trouble casting spell after spell, with no rest.
Magic Rule 3:While magic-based characters can absolutely use magic to fight instead of ki, and their abilities increase as they gain in power (under 80/60 rules, just like ki), keep in mind that shooting someone with a fireball is much less tiring than shooting someone with the bazooka you just created. The hardship of magic use scales with the attempted feat. Using Magic Materialization to conjure a hand-sized stone is easy peasy for most magicians. But conjuring a building-sized boulder would be extremely exhausting, even for a Kaioshin. Similarly, creating more complex materials and machinery will cause you to fatigue faster.
In short, the larger and/or more complex something is, the harder it is to conjure.
Magic Rule 4:You can only make what you know. The less familiarity you have with a thing, the harder it is to conjure. If someone is bragging to you about their new Baotendo gaming console, and you've never played Baotendo before, you're prolly going to have a real tough time conjuring one of your own.
Magic Rule 5:Anyone found in willful, blatant, and repeated disregard for these rules are subject to having their use of magic suspended or revoked permanently.